1. Field of Application
This invention relates to articulable joints; and more particularly, to joints rotatable about a predetermined axis of rotation between selective locked positions.
2. Description of the Prior Art
Articulable joints facilitate connecting two members together so that they can be moved with respect to each other about one or more predetermined axis of rotation. Some such joints are quite versatile permitting movement about plural axis of rotation; a first such axis of rotation; for example, passing through such members in a longitudinal direction; and a second such axis of rotation, for example, passing through such members in a transverse direction. Other articulable joints merely connect two members together for rotation about a single axis of rotation.
Many such articulable joints not only connect the two members together for selective positioning with respect to each other, but also provide means for locking or latching the joint in selected positions. Otherwise the weight of one or both such members, or something carried thereby, acting on the articulable joint will permit unwanted movement of one of such members with respect to the other (or both members with respect to each other). Some articulable joints are locked in position by friction type force application means, but many such locking means yield with time and wear and have failed to prove effective for the purpose. Other lockable articulable joints require the use of tools to release the lock. If the tool is not readily available, releasing the lock may become an inconvenience instead of a benefit of the joint.
Locking articulable joints are commonly utilized in lamp and lighting fixtures. Many lamps and lighting fixtures connect the lamp socket, into which the light bulb is screwed, to its carrying member (an arm or pole) by way of a joint that permits movement of the lamp socket about an axis of rotation perpendicular to an axis passing through the lamp socket carrying member. Quite often the lamp socket is disposed in a bullet or globe-like housing which is, in turn, connected to a carrying member by such a joint. Selective positioning of the housing, or bulb socket, of such units may require release of a locking device before being able to move the lamp unit, and subsequent tightening of the locking device after such movement if the lamp is to maintain its position. Quite often the locking device comprises friction type fittings which deteriorate with age and continued movement of the lamp carrying unit, and releasing and tightening of the locking device; or use of a screwdriver or other tool which is not readily available whenever the light needs re-positioning.